This invention relates generally to gas turbine engines, and more particularly, to gas turbine engines and methods of assembling the same.
Gas turbine engines typically include low and high pressure compressors, a combustor, and at least one turbine. The compressors compress air which is channeled to the combustor where it is mixed with fuel. The mixture is then ignited for generating hot combustion gases. The combustion gases are channeled to the turbine(s) which extracts energy from the combustion gases for powering the compressor(s), as well as producing useful work to propel an aircraft in flight or to power a load, such as an electrical generator.
During engine operation, a lubrication system is used to lubricate gas turbine engine components. For example, the lubrication system is configured to channel lubrication fluid to various bearing assemblies within the gas turbine engine. During engine operation, the temperature of the lubricating fluid increases undesirably. The increase in the lubrication fluid temperature is caused by heat generated by sliding and rolling friction of components like bearings, gears, and seals within a sump and also from heat-conduction through the sump walls due to hot air surrounding the sump enclosure. The lubrication fluid lubricates the components and removes heat from the components which results in an increased lubricant temperature.
To facilitate a reduction in the operational temperature of the lubrication fluid and cause the fluid to more effectively lubricate components and improve heat removal capability within the gas turbine engine, at least one known gas turbine engine utilizes a heat exchanger that is coupled to the engine proximate to the cowl region. More specifically, the heat exchanger is coupled to the engine within a channel that extends between the fan cowl and the core gas turbine engine. During operation, airflow is channeled through the heat exchanger to facilitate reducing the operational temperature of the lubrication fluid. However, since the airflow in the exhaust flowpath is at the same approximate relative pressure as the airflow in the inlet flowpath, the exhaust must be behind the throat of the fan nozzle. As such, when the gas turbine engine is operating during relatively low thrust conditions there is little pressure difference between the heat exchanger airflow inlet and the heat exchanger airflow outlet. To compensate for the relatively low airflow differential through the heat exchanger, at least one gas turbine engine includes a relatively large heat exchanger having a relatively large surface area to facilitate channeling an increased quantity of airflow through the heat exchanger to more effectively cool the lubrication fluid channeled therethrough. Accordingly, reducing the operating temperature of the lubrication fluid utilizing a known heat exchanger may increase the cost of the gas turbine engine assembly and may also increase the weight of the gas turbine engine assembly thus reducing overall engine efficiency.